Production of lightweight aggregate from molten slag



L. A. EDWARDS June 30, 1953 PRODUCTION OF LIGHTWEIGHT AGGREGATE FROM MOLTEN SLAG Filed April 26, 1951 l 1 I 1 l l l l l l l l l l I l l l l 1 l INVENToR.

Patented June 30, 1953 NITED STATS PAT-ENT OFFICE PRDUCTION F LIGI-ITWEIGHT AGGRE- GATE-FROM MOLTEN SLAG Lee A..Edwards, Sheffield, Ala., assignor to Tennessee Valley Authority, a corporation of the The invention vherein describe-d 'may be manufactured and used by or for the Government for governmental purposes without lpayn'lent to me of any royalty thereon.

This invention relates to improved apparatus for producing expanded or ica-med slag. It relates particularly to improved apparatus for in troducing steam into molten slag contained 'in a receptacle.

Giller, in United States Patent 1,483,76, has Lescribed a method and apparatus for expanding molten slag. His apparatus comprises a series of receptacles into each of which is introduced successively a `quantity of water and a quantity of molten slag. The hot slag converts the water into steam, which in turn eX- pands the slag into a frothy, porous material.

lAfter a short interval the expanded slag is discharged l:from these receptacles.

There are several disadvantages inherent vin the operation oi apparatus and methods in which molten slag is introduced into a receptacle containing a layer of water. initially, the volume of such molten slag is small as compared to the volume of water; thus, rather than being e'xe panded, the rst quantity or" slag so introduced is often quenched and granulated. Later, as larger quantities of slag cover the layer of water, the is irothed by the action of steam formed, but the product discharged from the receptacle is not uniform in structure, density, or in strength. Such lack or" uniformity detracts from the value of the product formed.

lt is an object oi this invention to provide an apparatus for uniformly expanding molten slag in a receptacle which utilizes heat from the molten slag for converting water into steam and which distributes and introduces the resulting steam into the molten slag in a uniform manner.

Another object is to provide such apparatus in which the means for distributing and introducing steam and cannot be blocked by small quantities of hardened slag.

Another object is to provide an apparatus having the particular advantageous arrangement of parts shown and described.

Other advantages will become apparent as this disclosure proceeds.

i have found that such apparatus may be formed by providing a receptacle or, preferably, a chain of water-tight receptacles, each having a false bottom having a plurality of openings therethrough; a plurality of loose-fitting plugs singly disposed through each of said openings, each of said plugs comprising a loose-iitting head .large enough 'to cover .one of said openings, a

shank portion 'having effective length slightly greater than the thickness `of said false bottom, and a retaining vmember attached to or integral with said shank'beneath .the false bottom; means 4for introducing 'water into .said receptacle beneath said false bottom; and means for subsequently introducing molten slag into said receptacle above said false bottom.

In the attached drawings Figure 1 is a sectional view of one type of such receptacle; Figure 2 is an enlarged detail of a short section oi the false bottom illustrated .in Figure l, showing the .relationship of one loose-fitting plug to an opening through the false bottom; and Figure 3 shows one preferred. type of construction in which a series 0f such .receptacles is arranged for use in a continuous process.

In Figure '1 the reference numeral l indicates a water-tight .receptacle which may be made in any suitable ksize and shape. A false bottom is disposed therein, supported upon shoulder ft and held in .place by bolts 5. A plurality Vof openings t3 through the false bottom are disposed substantially luniformly over the area thereof. Aplurality of loose-fitting plugs 6 are singly disposed through each of openings 3. Each of plugs 6 comprises a .loose-iitting head portion 2l large enough to cover opening 3, a shank portion 22 having effective length slightly greater than the thickness of V'false bottom 2, and a retain- 'ing member 23 below the false bottom, as is shown most clearly in the enlarged detail Figure 2. The head of plug 6, although large enough 'to 'cover opening A3, should be sufficiently loose- L iitting upon the surface of false bottom 2 to permit water to ilow easily beneath it. Such loose t is readily obtained by providing an irregular surface 24 upon the bottom of these heads or by curving the heads slightly. Plugs 6 may conveniently be made from common nails of suitable size inserted through openings 3 and having their Shanks bent to form an integral retaining member beneath false bottom 2. Suitable links 1 are preferably attached to or formed. integrally with receptacle I in position to cooperate with corresponding links of adjacent receptacles to form a chain of receptacles.

Figure 3 shows a number of such receptacles joined together to form an endless chain disposed upon rotatably mounted sprocket wheels 8, at least one of which is driven in any suitable manner from any convenient source of power (not shown). A water inlet 9 is disposed to introduce a controlled quantity of water into n each receptacle as it is turned into upright position by rotation of sprockets 8. Inlet 9, the loose-tting heads of plugs 6, and openings 3 co operate to form a means for introducing water into that part of each receptacle below false bottom 2. A means for introducing molten slag into each receptacle, which is preferably a slag trough I9, is disposed subsequent to water inlet 9 in the direction of travel of the chain.

In operation sprockets 8 are set in motion and each receptacle passes under water inlet 9. This inlet is of such predetermined size or properly valved so that the amount of water introduced into each receptacle is suflicient to fill the cham* ber below false bottom 2 and to just cover the false bottom. The water introduced runs into the lower chamber because of the loose nt of the heads of plugs 6 upon the upper surface of the false bottom.

Each receptacle then passes in turn beneath slag trough I and receives therefrom a quantity of molten slag sufficient to substantially ll that part of the receptacle above false bottom 2 when fully expanded. Heat from the slag vapor izes the water below false bottom 2 and steam pressure builds up in the lower chamber. Resulting steam pressure lifts plugs 5 with the result of emitting puffs of steam into the body of molten slag. I have found that so long as steam is being rapidly generated in the lower chamber a violent, rapid, vertical reciprocal motion is imparted to plugs 6, somewhat analogous to the ac tion of the plunger of an air hammer. The introduction of a great number of small puffs of steam from openings evenly distributed beneath the body of slag eifectively expands the slag into a uniform foam-like state. The motion of plugs 6 also effectively prevents obstruction of openings 3 by small quantities of hardened slag.

The chain of receptacles is made long enough that the expanded slag is retained in each receptacle until it has hardened, or at least until a crust has formed on the top, bottom, and sides of the mass. As each receptacle is turned in passing over the second sprocket 8 the resulting mass of cooled expanded slag Il drops out of the receptacle into any suitable receiving space.

The height at which the perforated false bottom is placed above the bottom of the receptacle depends upon the depth of the receptacle. For most effective results the amount of Water added to each receptacle should be slightly greater than the 4amount that can be evaporated by the molten slag. In tests of my apparatus, in which slag produced in electric-furnace smelting of phosphate rock was used, it was found that a lower chamber filled with water having a depth of about 21/2 inches was appropriate for expanding the slag to a depth of 15 inches. In general, satisfactory results may be obtained by spacing the perforated false bottom from the bottom of the receptacle a distance equal to about one-eighth to one-sixth of the depth of the receptacle.

Apparatus as described above will ordinarily be more efficient and convenient in operation for most commercial uses than its batch-type equivalent. The latter may be used in some particular -applications if desired. All that is necessary is to provide a receptacle equipped with a false bottom, openings, and plugs as described above, any suitable means for filling its lower chamber with water, and means for subsequently introducing slag above the false bottom.

I claim as my invention:

l. In a device for expanding slag the combination of a water-tight receptacle; a false bottom Ihaving a plurality of openings therethrough disposed in said receptacle; a plurality of loose-ntting plugs singly disposed through each of said openings, each of said plugs comprising a loosefitting head large enough to cover one of said openings, a shank having effective length slightly greater than ,the thickness of said false bottom, and a retaining member attached to said shank beneath the false bottom; means for introducing water into said receptacle; and means for introdueing molten slag into said receptacle above said false bottom.

2. In a device for expanding slag the combination of a Water-tight receptacle; a false bottom having a plurality of openings therethrough disposed in said receptacle; a plurality of nails singly disposed through each of said openings, each of said nails having a head large enough to cover one of said openings disposed above said false bottom and having its shank bent into re taining relationship a short distance beneath said false bottom; means for introducing water into said receptacle; and means for introducing molten slag into said receptacle -above said false bottom.

LEE A. EDVJARDS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,453,735 Twining May l, 1923 1,843,716 Giller Feb. 2, 1932 2,061,830 Campbell Nov. 24, 1936 2,428,249 Stuart et al Sept. 30, 1947 

